Acceptance testing of production items often includes environmental testing, such as pressure testing. For example, a pressure vessel or other production item may be pressurized to verify integrity.
Typical current pressure test processes utilize dry nitrogen (N2) gas to pressurize a unit under test. N2 gas is used instead of water in order to maintain internal cleanliness of the unit under test (UUT).
As is known, in a closed gaseous system when pressure increases, temperature also increases. As a result, during a pressurization cycle of pressure testing the N2 gas may heat up to temperatures that exceed engineering design temperature limits of the UUT. As is also known, in a closed gaseous system conversely when pressure decreases, temperature also decreases. As a result, during a depressurization cycle of pressure testing the N2 gas temperature may drop below engineering design temperature limits for the UUT. Such temperature excursions can induce undesirable thermal stresses.
For a pressure vessel, exceeding engineering design temperature limits may causes severe consequences. For example, the temperature excursion may go beyond brittle fracture prevention limits (BFPL) on temperature for a given pressure. In such a case, operational lifetime of the pressure vessel may be shortened (that is, a number of allowed pressurization cycles may be limited). Otherwise, the BFPL may be even more constrained to accommodate the same operational lifetime but to insert an extra design safety margin into the pressure vessel.
As a result, it would be desirable to control temperature excursions during pressure testing. One currently known method for controlling temperature excursions during pressure testing reduces the rates of pressurization and depressurization. However, this currently known method results in lengthy cycle times for the pressure testing process. For example, each pressurization/depressurization cycle of a pressure test may take over an hour. In some pressure test scenarios where five or so pressurization/depressurization cycles are performed, the entire pressure test can take over five hours. In another known method, forced air cooling is applied to the UUT during pressurization. While this technique addresses heating during pressurization, the depressurization cycle must still be slowed as described above.
As a result, it would be desirable to mitigate temperature excursions during pressure testing without inserting excessive delays into the pressure testing process. However, there is an unmet need in the art for a system and method for mitigating temperature changes during pressure testing without inserting excessive delays into the pressure testing process.